Two researchers from Duke University say that installing solar cells on roofs saves a lot of water and also cuts down on greenhouse gas emissions that contribute to global warming. They discovered that a household could save an average of 16,200 gallons of water annually by installing solar panels on the roof. In some states, such as California, this savings can reach 53,000 gallons, or 60 percent of the average U.S. household’s water consumption.
The savings will not be reflected in your water bill, but they are still significant.
This is because energy consumption and water consumption are intrinsically linked. The production of electricity in the United States consumes nearly as much water as agriculture. This number does not, however, include the extra water that is used to make fossil fuels and deal with coal ash waste.
Avner Vengosh, a distinguished professor of environmental quality at Duke University‘s Nicholas School of the Environment and co-author of a new paper published in Science of the Total Environment on Sept. 19, said, “To make electricity for the grid, we must mine and burn coal, frack and pump natural gas, and cool nuclear plants. All of these processes use large amounts of water that are constantly lost.”
However, manufacturing a solar cell requires a one-time use of a much smaller volume of water, as Vengosh explained. “After installation, there will be no water usage from that source for the next 25 years of expected use.”
At the moment, more than 70% of the world’s solar panels are made in China. This means that the water used to make solar energy comes from places other than China.
Professor of environmental policy at the Nicholas School and co-author Erika Weinthal said that the whole global supply chain needs to be looked at to understand how making solar panels affects water around the world.
“From a contamination standpoint, solar cells pose a significant threat to the environment,” Vengosh stated. It contains heavy metals, some of which are extremely toxic, and, as a result, they may have an impact on the environment in which the product is manufactured.
After that, however, solar water consumption is zero.
Previous research has attempted to evaluate the amount of water used at various stages of energy production, typically expressed as the ratio of water volume to energy, such as liters or gallons per gigajoule. In the new study, the authors added up all of the energy sources used to make electricity for homes in the contiguous U.S. and turned that number into the amount of water each state uses.
The new study calculated the virtual water consumption of each home in 48 states after analyzing the statewide water consumption in the residential sector. Based on these estimates, homes in the United States use 2,600,000,000,000,000,000,000 gallons of water each year.
Converting residential properties to solar energy reduces both grid electricity consumption and water consumption. In some states, such as the southwestern United States, residential rooftop solar installations can result in water savings of up to one thousand percent.
These calculations are a follow-up to a book that Vengosh and Weinthal wrote earlier this year about how energy and water quality affect each other. The book gives a complete baseline for how much water different fossil fuel sources use.
During the pandemic shutdown, the authors chose to install solar panels on their shared residence. Initially, the primary motivation was to reduce carbon emissions, but after some time, they realized it could also save water.
“This article is a direct result of our desire to decarbonize our personal lives,” Weinthal explained. “I teach global environmental politics and the Paris agreement, and I always encourage my students to make the connection between what is occurring at the interstate level and what we can do with our own forms of agency.”
Today, photovoltaic solar cells produce approximately 1.5% of the nation’s electricity. The authors estimate that this represents an annual savings of 99 billion gallons of water, or roughly four days of California’s total water consumption. As the solar percentage increases, however, so will the savings.
per also compares water consumption for energy by state, given that each state uses different energy sources for electricity generation and has different usage patterns and home populations.
Vengosh stated that the New England states have a lot to gain by switching to solar energy because they use little electricity for air conditioning and heat their homes with oil rather than electricity. Arizona and California, which have a lot of sunny days but not enough water, would also be big winners.
In their book, Weinthal and Vengosh demonstrate that water consumption is only one aspect of the problem. The contamination of water resources as a result of coal mining, hydraulic fracturing, and coal ash disposal further reduces the availability of water. Consequently, the water footprint of extracting fossil fuels is much greater than we realize.
“We also attempted to quantify water quality effects, such as the amount of water contaminated by an oil spill or the chronic disposal of coal ash into water resources,” Vengosh said. Therefore, if you know the volume of the oil spill, you can calculate the amount of contaminated and lost water.
According to Weinthal, assessing the total price of any technology is crucial. “We must move toward renewable energy sources such as solar and wind, but in doing so, we must recognize that any energy infrastructure, renewable or not, may incur water-related costs. “Every form of energy production requires consideration of its water footprint,” she said,
The researchers have already turned their attention to how much water lithium mining uses and how it affects the environment. Lithium is an important metal for making batteries for the next generation.
